Move error in-crate

We'll operate under the assumption that postgres will end up being a
wrapper on top of tokio-postgres so postgres-shared goes away.

Author: sfackler

tokio-postgres/Cargo.toml

@@ -39,6 +39,7 @@ futures = "0.1.7"
 futures-cpupool = "0.1"
 lazy_static = "1.0"
 log = "0.4"
+phf = "=0.7.22"
 postgres-protocol = { version = "0.3.0", path = "../postgres-protocol" }
 postgres-shared = { version = "0.4.0", path = "../postgres-shared" }
 state_machine_future = "0.1.7"